Download - Magnetic Poles
Magnetic Poles
• Like poles repel
• Opposite poles attract
• North pole
• South pole
Magnetic Force
• 1) Between magnets, it is the attraction of unlike magnetic poles and the repulsion of like magnetic poles
• 2) Between a magnetic field and moving charge, it is the deflecting force due to the motion of the charge
Difference between magnetic poles and electron charges
• Electric charges can be isolated– Protons and electrons can exist separately
• Magnetic poles cannot– North magnetic poles can’t exist without south poles
• If you break a magnet in half, each half will act as a magnet
• If you break that piece in half, you will then have four magnets
• This suggests that the atoms themselves are magnets
Magnetic Field
• The region of magnetic influence around a magnetic pole or a moving charged particle
• Field of force
Motion of electric charges
• Electron spinning
• Electron revolution around the protons
Electron spinning• An electron spinning creates a magnetic field
• A pair of electrons spinning in the same direction creates a stronger magnet
• A pair of electrons spinning in the opposite direction work against each other
Metals• Materials such as iron, nickel, and cobalt have
electrons whose spins do not cancel out
• Iron has four paired electrons that can have the same spin
Magnetic domains
• Clusters of atoms line up with one another
Permanent Magnet
• Place a piece of iron (or a similarly magnetized material) in a strong magnetic field
• Moving charge produces a magnetic field
• A current of charge produces a magnetic field
Electromagnetic Induction
• Electric current can be produced in a wire simply by moving a magnet into or out of a coil of wire
• A voltage is induced by the relative motion between a wire and the magnetic field
Faraday’s Law
• The induced voltage of a coil is proportional to the number of loops multiplied by the rate at which the magnetic field changes within those loops
• More practical to move the coil then move the magnet
• Generator has a rotating coil in a stationary magnetic field
• Converts mechanical energy into electrical energy
• http://video.google.com/videoplay?docid=3902466783636795302#
Any Questions?